Stretchable laminates are used in a number of personal care products to enable the products to conform to a wearer's body for enhanced fit and, in some cases, leakage protection. Conventional stretchable laminates typically have one layer of elastomeric material, or at most two layers of elastomeric material that are integrated upon extrusion and are not handled separately in a “green” state before being integrated into the laminate. By using only one layer of elastomeric material, or a combination of elastomeric materials each pre-formed prior to forming the stretchable laminate, the stretch capabilities of the resulting laminate are significantly limited.
One technique for enhancing the stretchability of laminates is achieved through the use of necked materials. The terms “necked” and “neck stretched” are used interchangeably to describe material, such as a nonwoven web or a laminate, that is drawn or stretched in a lengthwise direction thereby reducing its width or its transverse dimension. The controlled drawing may take place under cool temperatures, room temperature or greater temperatures and is limited to an increase in overall dimension in the direction being drawn up to the elongation required to break the material, which in many cases is about 1.2 to 1.6 times. When relaxed, the material does not return totally to its original dimensions. The necking process typically involves unwinding a sheet from a supply roll and passing it through a brake nip roll assembly driven at a given linear speed. A take-up roll or nip, operating at a linear speed higher than the brake nip roll, draws the material and generates the tension needed to elongate and neck the material.
In general, a neck bonded laminate includes an elastomeric film or filaments joined to a necked material in at least two places. The elastomeric film or filaments may be joined to the necked material at intermittent points or may be completely bonded to the necked material. The joining is accomplished while the elastic film or filaments and the necked material are in a juxtaposed configuration. The resulting neck bonded laminate is elastic in a direction generally parallel to the direction of neckdown of the necked material, and may be stretched in that direction to the breaking point of the necked material or elastic material. Neck bonded laminates are described in greater detail in U.S. Pat. No. 5,336,545 issued to Morman, which is hereby incorporated by reference in its entirety in a manner consistent with the present document.
Another type of stretchable laminate is a vertical filament laminate made using a Vertical Filament Lamination (VFL) process, which is described in PCT Publication WO01/87589, published 22 Nov. 2001, and entitled ELASTIC STRANDED LAMINATE WITH ADHESIVE BONDS AND METHOD OF MANUFACTURE by H. M. Welch et al., incorporated herein by reference. This process entails vertically extruding multiple filaments onto a quench roll, elongating the filaments, laminating the filaments to a contractible (e.g. bonded carded) web and then letting the filaments contract thus creating, for example, an elastomeric high-loft bonded carded web.
Neck bonded laminates and vertical filament laminates each have attributes distinct from one another. Namely, neck bonded laminates are cross-direction stretchable, whereas vertical filament laminates are machine-direction stretchable. It may be desirable to have the capability to manufacture both neck bonded laminates and vertical filament laminates in the same location. However, even though the same types of materials can be used to produce each of these types of laminates, different types of apparatus are required to manufacture each of these types of laminates. Thus, significant capital and material costs are expended in building and maintaining separate machines for the neck bonded laminate and the vertical filament laminate production lines.
While neck bonded laminates and vertical filament laminates are suitable for a number of uses, certain applications could benefit from stretchable laminates having additional stretch characteristics.
There is thus a need or desire for stretchable laminates having enhanced stretchability, and a method of making such stretchable laminates.
There is a further need or desire for a single machine that is capable of producing both neck bonded laminates and vertical filament laminates, as well as neck stretched bonded laminates (NSBL's) such as taught in U.S. Pat. No. 5,116,662 issued to Morman, which is hereby incorporated by reference in its entirety in a manner consistent with the present document.